Warm water treatment in combination with modified atmosphere packaging reduces undesirable effects of irradiation on the quality of fresh-cut iceberg lettuce

Fresh-cut iceberg lettuce dipped in either 5 or 47 degrees C water for 2 min was packaged in modified atmosphere film bags and then exposed to 0, 0.5, 1, or 2 kGy gamma-radiation. Dipping cut lettuce in 47 degrees C water for 2 min prior to irradiation reduced antioxidant and phenolic accumulations induced by irradiation. Irradiation at 2 kGy increased cellular leakage and sogginess of cut lettuce dipped in both temperatures. Samples irradiated at 0.5 and 1 kGy had similar firmness and vitamin C and antioxidant contents as the controls after 14 and 21 days of storage except 1 kGy samples dipped at 47 degrees C had lower antioxidant contents than controls at 14 days of storage. Lettuce dipped at 47 degrees C and irradiated at 0.5 and 1 kGy had better overall visual quality and less tissue browning than corresponding irradiated samples dipped at 5 degrees C. These results suggest lettuce treated with warm water and irradiated at 0.5 or 1 kGy had the best sensory quality without significant loss in texture, vitamin C, or total antioxidants.     

红富士苹果自发气调保鲜技术研究

采用5种不同保鲜膜包装，在0℃和10℃条件下，研究不同改性聚乙烯保鲜膜和聚氯乙烯保鲜膜、包装量对红富士苹果自发气调贮藏保鲜效果与原理，为红富士苹果冷藏保鲜和保鲜膜筛选提供依据。结果表明：不同红富士苹果保鲜膜包装内10 d左右O₂和CO₂浓度达平衡值。0℃条件下不同包装的O₂平衡值为12%～19%，CO₂为1.8%～5.0%，10℃条件下不同包装的O₂平衡值为5%～16%，CO₂为3.5%～8.0%。同样条件下2#保鲜膜包装内O₂最低、CO₂最高。各保鲜袋内虎皮病发生率高低顺序为：2#＞1#＞3#＞5#。包装量越大，温度越高，虎皮病发生率越大、乙醇和乙醛含量越高。利用富士专用保鲜膜和适宜的PE保鲜膜包装贮藏7个月，红富士苹果质量商品价值基本不变。     

The role of packaging film permselectivity in modified atmosphere packaging

Modified atmosphere packaging (MAP) is commercially used to increase the shelf life of packaged produce by reducing the produce respiration rate, delaying senescence, and inhibiting the growth of many spoilage organisms, ultimately increasing product shelf life. MAP systems typically optimize O(2) levels to achieve these effects while preventing anaerobic fermentation but fail to optimize CO(2) concentrations. Altering film permselectivity (i.e., beta, which is the ratio of CO(2)/O(2) permeation coefficients) could be utilized to concurrently optimize levels of both CO(2) and O(2) in MAP systems. We investigated the effect of modifying film permselectivity on the equilibrium gas composition of a model MAP produce system packaged in containers incorporating modified poly(ethylene) ionomer films with CO(2)/O(2) permselectivites between 4-5 and 0.8-1.3. To compare empirical to calculated data of the effect of permselectivity on the equilibrium gas composition of the MAP produce system, a mathematical model commonly used to optimize MAP of respiring produce was applied. The calculated gas composition agreed with observed values, using empirical respiration data from fresh cut apples as a test system and permeability data from tested and theoretical films. The results suggest that packaging films with CO(2)/O(2) permselectivities lower than those commercially available (<3) would further optimize O(2) and CO(2) concentration in MAP of respiring produce, particularly highly respiring and minimally processed produce.     

气调包装技术用于虾皮保鲜的效果研究

为改进虾皮贮藏质量,延长货架期,研究了气调包装(Modified Atmosphere Packaging)对虾皮的保鲜效果。采用3种不同浓度配比的N₂和CO₂气体和真空包装等方法对虾皮进行包装,分别于5℃、室温和35℃下贮藏。检测虾皮感观、色差、菌落总数和脂肪含量。结果表明：低温有利于虾皮保鲜,高浓度CO₂气调贮藏能抑制虾皮中的微生物繁殖,减缓脂肪蚝蛤败速度,但CO₂浓度过高易使虾皮产生异味,影响感观品质。气调与低温结合可延长虾皮的保鲜期2个多月,推荐的气调气体比例为70%N₂/30%CO₂,低温冷藏。     

Molecular design of antibrowning agents

Tyrosinase inhibitory and antioxidant activity of gallic acid and its series of alkyl chain esters were investigated. All inhibited the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) catalyzed by mushroom tyrosinase. However, gallic acid and its short alkyl chain esters were oxidized as substrates yielding the colored oxidation products. In contrast, the long alkyl chain esters inhibited the enzyme activity without being oxidized. This indicates that the carbon chain length is associated with their tyrosinase inhibitory activity, presumably by interacting with the hydrophobic protein pocket in the enzyme. On the other hand, the esters, regardless their carbon chain length, showed potent scavenging activity on the autoxidation of linoleic acid and 1,1-diphenyl-2-p-picryhydrazyl (DPPH) radical, suggesting that the alkyl chain length is not related to the activity. The effects of side-chain length of gallates in relation to their antibrowning activity are studied.     

薄膜气调包装对枇杷果实冷藏期间呼吸和品质性状的影响

通过对呼吸速率、总可溶性固形物、可滴定酸、pH值、果肉硬度、维生素C、失重率和品质及感官指标的变化进行分析，研究了薄膜气调包装对枇杷(Eriobotrya japonica Lindl.，品种：解放钟）果实冷藏期间呼吸和品质特性的影响，气调包装用的薄膜为低密度聚乙烯薄膜(LDPE，厚度20 μm)，以打孔的低密度聚乙烯薄膜包装为对照。结果表明，低密度聚乙烯薄膜包装枇杷果实后，3～4 d后可维持一个相对稳定的适宜枇杷贮藏的O₂和CO₂的气体浓度，即CO₂(4.8±0.67)%，O₂(11.5±0.85)%；薄膜气调包装结合低温可明显地降低枇杷果实的呼吸速率；薄膜气调包装可以最大限度地减小冷藏期间的枇杷果实的失重率、果肉硬度、维生素C、总可溶性固形物、可滴定酸和固酸比的变化，维持枇杷的新鲜品质，延长货架期。因此，低密度聚乙烯薄膜（LDPE，厚度20 μm）气调包装可用于枇杷的贮藏保鲜。     

Antioxidant content of fresh-cut pears stored in high-O2 active packages compared with conventional low-o2 active and passive modified atmosphere packaging

The antioxidant content of fresh-cut 'Flor de Invierno' ( Pyrus communis L.) pears dipped into a 0.75% w/v N-acetylcysteine + 0.75% w/v glutathione solution and packaged under 70 kPa of O2 atmospheres (HOA) was evaluated as an alternative to actively modified low-O2 atmosphere (LOA) and passively modified atmospheres (PA). Changes in color, vitamin C, individual phenolic compounds, and antioxidant activity of fresh-cut pears as well as in O2, CO2, and ethylene headspace concentrations inside the packages were assessed for 14 days at 4 degrees C. Not only did the use of antioxidants prevent browning and reduce ethylene production of fresh-cut pears, but also their application under LOA best maintained vitamin C, chlorogenic acid, and antioxidant capacity compared with HOA. The results show that the use of glutathione and N-acetylcysteine enhanced the formation of phenylpropanoids in fresh-cut pears stored under LOA.     

气调包装对松籽常温贮藏生理和品质变化的影响

以朝鲜红松带壳松籽和去壳松仁为试材,将其分别放在30 μm紫色聚氯乙烯袋、30 μm白色聚氯乙烯袋和40 μm白色聚乙烯袋中进行自发气调贮藏,研究了常温下（20～30℃）贮藏180 d期间松籽种仁的生理、品质和脂肪酸氧化变化。结果表明：与40 μm聚乙烯袋相比,30 μm紫色聚氯乙烯袋与30 μm白色聚氯乙烯袋可以形成相对低O2高CO2的贮藏条件,能有效降低带壳松籽和去壳松仁的呼吸速率和可溶性总糖的损耗,提高种仁的贮藏优品率;同时可以较好地防止总脂肪的降解,抑制酸价、过氧化值的升高和碘价的降低。综上所述,30 μm聚氯乙烯袋可以较好地保持松籽品质,相同气调包装贮藏下带壳松籽的贮藏品质优于去壳松仁。     

贮藏温度和气调包装对鸡蛋保鲜效果的影响

为了延长鸡蛋保鲜期,研究在室温(25℃)和冷藏(4℃)条件下不同配比CO2、O2、N2三元混合气体包装对鸡蛋保鲜效果影响,结果表明:鸡蛋采用气体组分为50％CO2、7％～11％O2、39％～43％N2的气调包装贮藏保鲜,室温下贮藏30d仍保持AA级,而不包装室温贮藏30 d降到了B级;不包装冷藏也可延长鸡蛋保鲜期,但失重率相对较高;气调包装与冷藏结合对鸡蛋的保鲜效果不是2种处理的保鲜效果之和,与气调包装室温贮藏的保鲜效果相似.50％CO2、7％～11％O2、39％～43％N2三元气体包装、室温贮藏可实现鸡蛋就地贮藏,试验为鸡蛋贮藏保鲜提供参考.     

1-MCP处理和气调包装对枸杞鲜果低温贮藏品质的影响

为比较1-甲基环丙烯(1-methylcyclopropene,1-MCP)处理和2种气调包装对枸杞鲜果保鲜的效果,研究了1.0μL/L的1-MCP处理、聚乙烯膜气调包装(polyethylene film modified atmosphere packaging,PEF-MAP)和硅窗膜气调包装(silicon gum filmMAP,SGF-MAP)对枸杞鲜果(2±1)℃下贮藏品质和生理特性的影响。结果表明,1-MCP处理可减轻枸杞果实贮藏末期感官酸腐味,但对可滴定酸和果皮颜色等没有显著影响(P>0.05)。聚乙烯膜气调包装和硅窗膜气调包装可保持果实可溶性固形物质量分数,提高固/酸比及表皮状况、香气、质地等感官品质,但加快了可滴定酸的下降,对颜色、感官液汁变化影响不明显(P>0.05)。在贮藏末期(第35天),3个处理分别可将枸杞果实腐烂率由46.7%降低至31.1%、8.9%和26.7%。气调包装对枸杞的贮藏效果好于1-MCP处理,其中,聚乙烯膜气调包装效果较佳,可将枸杞果实贮藏期延长14d。试验结果可为鲜食枸杞商业化贮藏提供参考。     

Oxyresveratrol as an antibrowning agent for cloudy apple juices and fresh-cut apples

Antibrowning activities of Morus alba L. twig extracts, oxyresveratrol, and mulberroside A isolated from mulberry twig on cloudy apple juices and fresh-cut apple slices were evaluated by monitoring the change of a* value, total color difference (DeltaE), and visual observation. It was found, similar to 4-hexylresorcinol, that oxyresveratrol could effectively inhibit browning in cloudy apple juices at a concentration as low as 0.01% and that mulberry twig extract also showed remarkable antibrowning effects on cloudy apple juices. However, for fresh-cut apple slices, mulberry twig extract and oxyresveratrol needed to be used in combination at least with ascorbic acid to exhibit their antibrowning effects. Apple slice samples treated by dipping in a solution containing 0.001 M oxyresveratrol, 0.5 M isoascorbic acid, 0.05 M calcium chloride, and 0.025 M acetylcysteine did not undergo any substantial browning reaction for 28 days at 4 degrees C. However mulberroside A did not show antibrowning effects on cloudy apple juices although it is also a good mushroom tyrosinase inhibitor.     

果蔬气调包装理论研究进展

气调包装是一种可延长新鲜水果货架寿命的重要技术。气调包装的质量主要取决于包装内气体成分、温湿度的调节。建立气调包装的理论模型是保证气调包装质量、进行气调包装系统设计的关键。该文综述了国内外这方面的研究成果,着重论述了果蔬呼吸模型、呼吸速率的测定方法、包装内外气体交换模型、包装内温度与湿度变化数学模型,并分析了目前研究存在的不足,为果蔬气调包装的深入研究提供参考。     

Browning evaluation of ready-to-eat apples as affected by modified atmosphere packaging

The color and polyphenol oxidase (PPO) activity of fresh-cut Golden delicious apples were evaluated throughout cold storage under modified atmospheres. The shelf life of cut apples was extended to several weeks, especially when an initial atmosphere of 90.5% N(2) + 7% CO(2) + 2.5% O(2) and plastic pouches of 30 cm(3)/cm(2) x bar x 24 h were used. Under these conditions, a maximum 62% PPO activity depletion was observed. In all cases, the faster the initial PPO activity decays, the less the color changes. A fractional conversion first-order model was proposed for predicting color changes in minimally processed apples. Browning was better described through lightness (L) (k(L) = 0.017 - 0.07 day(-1)) and color difference (Delta E*) values (k(Delta E) = 0.015 - 0.073 day(-1)), which fitted the model with enough accuracy.     

气调包装条件下果蔬呼吸强度模型的研究进展

该文综述了国内外近几十年来气调包装(MAP)条件下果蔬呼吸强度模型的研究情况。探讨了在一定的贮藏时间内果蔬呼吸强度与袋内氧气浓度、二氧化碳浓度和温度的关系以及利用计算机技术进行MAP的最佳设计等方面的问题,从而为MAP技术更好地应用于果蔬保鲜提供参考。     

甜高粱茎秆采后生理特性及其自发气调包装贮藏的研究

为延长甜高粱茎秆贮藏期,研究了甜高粱茎秆采后呼吸速率、蔗糖转化酶、多酚氧化酶等变化规律,并用不同厚度的低密度聚乙烯薄膜(LDPE)进行了自发气调包装(MAP)贮藏试验.结果表明,甜高粱茎秆采后呼吸速率随温度升高而增大,温度从10℃上升到30℃,呼吸速率升高2倍左右;在相同温度下,辽甜一号茎秆的呼吸速率高于辽饲杂一号茎秆的呼吸速率.辽甜一号茎秆在O2 2.2%、CO2 7.6%下贮藏10 d,辽饲杂一号茎秆在O2 3.6%、CO2 6.4%下贮藏17 d会发生厌氧呼吸.甜高粱茎秆内中性、酸性蔗糖转化酶和多酚氧化酶在MAP贮藏中活性呈上升趋势,贮藏至30 d,总糖有2.8%～20.9%的损失,还原糖升高134.3%～523.1%,茎秆失重率为1.37%～1.51%.甜高粱茎秆在厚度为0.034 mm的低密度聚乙烯包装中蔗糖转化酶和多酚氧化酶活性增加幅度较小,总糖损失减少.该项研究为解决甜高粱茎秆制取燃料乙醇过程中的茎秆贮藏问题提供了科学的参考.     

适宜气调包装延缓冷藏鲳鱼品质变化延长货架期(英文)

该文主要研究了不同气体比例组分的气调包装处理对冷藏鲳鱼贮藏期间品质变化及货架期的影响,从中找出能使鲳鱼冷藏货架期延长的适宜气体比例。将新鲜鲳鱼以冰藏方式快速运至实验室,将样品经去头、去尾、去内脏处理后,分别置于3种气体组分条件(MAP1:20%CO2/80%N2,MAP2:50%CO2/50%N2,MAP3:80%CO2/20%N2)的气调包装袋内冷藏(4±1)℃保鲜,以空气包装样品作为冷藏对照组(AIR),其中包装袋内的气体与样品体积比为3∶1,在12 d内隔天测定各组样品的感官指标、微生物指标(菌落总数)与化学指标(挥发性盐基氮值、K值、三甲胺值与p H值)变化。冷藏后的第4天,对照组与气调处理组的感官分值、菌落总数、挥发性盐基氮值与三甲胺值差异显著(P0.05),冷藏对照组样品的各项指标首先达到新鲜限值,其冷藏货架期仅为4-5d。经过气调处理后的鲳鱼样品,其菌落总数达到二级鲜度的速度明显缓于冷藏对照组,其他各项指标的变化也证实了气调包装的潜在优点。其中,80%CO2+20%N2处理组能明显延缓样品p H值、挥发性盐基氮值、菌落总数、三甲胺值与K值的升高(P0.05),较冷藏对照组相比,其冷藏货架期能延长6~8 d。同时,气调处理组贮藏期间的p H值未呈现先降后升的变化规律,表明p H值不适用于评价气调包装鲳鱼贮藏期间的品质变化。气调包装样品的菌落总数在贮藏前期略有下降,表明CO2对样品菌落总数的升高有较好的抑制作用。在CO2≤80%条件下,各项微生物与理化指标的测定结果显示出不同气体比例的气调包装处理对冷藏鲳鱼的保鲜效果,CO2浓度越高,其保鲜效果越显著,气调处理能使鲳鱼样品的冷藏保鲜期由4 d延长至6-12 d,其中80%CO2+20%N2的气调处理组对鲳鱼样品的冷藏货架期延长效果较佳。     

天然保鲜剂与气调包装对牛肉火腿切片货架期的影响

该文以真空包装组为对照,在9℃、光照贮藏条件下,采用天然保鲜剂和气调包装对牛肉火腿切片进行了保鲜试验。结果表明：真空包装组(对照组)中的乳酸菌数量上升很快,28 d时就已大大超过6.70 log(cfu·g)^-1。随着乳酸菌的生长繁殖,各处理组产品的pH值不断下降。气调包装(60%CO₂+40%N₂)未显示出明显的抑菌作用,气调包装产品的a^*值(红度)随着贮藏时间的延长显著下降(p<0.05),褪色明显。天然保鲜剂(150 mg/kg Nisin+0.3%茶多酚)对乳酸菌有很好的抑制作用,采用切片后浸渍方式比腌制前添加方式的效果更好,能够延长牛肉火腿切片的货架期,保鲜剂对产品a^*值影响不明显(p＞0.05)。天然保鲜剂、气调包装对硫代巴比妥酸反应物(Thiobarbituric acid reactive substances, TBARS)变化的影响都不大(p＞0.05)。     

高氧气调包装对不同品种冷却猪肉贮藏品质及持水性的影响

为了研究不同品种冷却猪肉在高氧气调包装贮藏过程中,蛋白氧化对猪肉品质及持水性的影响,试验以氟烷基因(NN)型杜长大三元杂交猪和不含NN基因型的三门峡黑猪为研究对象,分析了2个品种猪肉经高氧气调包装(80%O2+20%CO2),于(4±1)℃下贮藏过程中肌肉色泽、蛋白质氧化、水分分布、保水性以及肌肉微观结构的变化。结果表明,随着贮藏时间的延长(0~10 d),2个品种猪肉的肌原纤维蛋白羰基含量显著升高(P0.05),巯基含量显著降低(P0.05),表明猪肉肌原纤维蛋白的氧化程度随着贮藏时间的延长而加剧;肌原纤维蛋白发生持续性氧化,肌原纤维蛋白骨架的完整性遭到不同程度破坏,肌束膜破裂,纤维束间隙增大,结构疏松,保水性降低,不易流动水逐渐态变为自由水;与贮藏初始相比,第3天时杜长大三元杂交猪和三门峡黑猪的不易流动水均显著降低(P0.05),第5天杜长大三元杂交猪的自由水显著增加(P0.05),而黑猪的自由水在第10天时显著性增加(P0.05);贮藏5 d以上时,2个品种猪肉的蒸煮损失率均较对照组的蒸煮损失显著增大(P0.05);2个品种猪肉的L*值、a*值、b*值均呈现先增加再降低的趋势,L*值在第7天时达到最大值,a*值在第3天时达到最大值,杜长大三元杂交猪和黑猪的b*值分别在第5天和第7天时达到最大值;2个品种的猪肉经高氧气调包装,其色泽、蛋白质氧化、水分态变、保水性、微观结构等指标变化规律相似,表明高氧气调包装对2种猪肉的贮藏品质及持水性的影响效应具有一致性。研究结果为高氧气调包装冷却猪肉贮藏品质及汁液流失控制提供依据。     

不同气调包装对冷藏鱼糜制品品质的影响

为分析不同气调包装对鱼糜制品冷藏过程中品质的影响,研究以鱼糜制品中的鱼丸为对象,通过测定其在 （0±0.5）℃冷藏过程中的菌落总数、理化和感官等指标的变化,评价气调包装的保鲜效果。气调包装条件分别为空气包装（对照）、低氧气调包装（60%CO2+10%O2+30%N2,均为体积分数,下同）、无氧气调包装（60%CO2+40%N2）、含保鲜剂的无氧气调包装（60%CO2+40%N2+保鲜剂）。结果表明,0℃下鱼丸在空气包装下贮藏32 d和低氧气调包装下贮藏42 d后菌落总数分达到8.7×104 cfu/g和8.5×104 cfu/g,超过规定的卫生标准;而无氧气调包装可使鱼丸的货架期达到47 d（菌落总数4.3×104 cfu/g）以上,含保鲜剂的无氧气调包装可使鱼丸货架期延长至52 d（菌落总数0.98×104 cfu/g）以上,并且能降低脂肪氧化程度;两组无氧气调包装样品在冷藏期间其pH值、TBA（硫代巴比妥酸）值和感官等指标都优于低氧气调包装和空气包装。无氧气调包装或结合生物保鲜剂包装能更好地延长冷藏鱼丸的货架期。     

生物保鲜剂结合气调包装对带鱼冷藏货架期的影响

为了延长带鱼冷藏货架期,以空气包装组为对照,在（4±1）℃冷藏条件下,采用复合生物保鲜剂涂膜及保鲜剂结合气调包装对带鱼进行保鲜试验。以感官评分、细菌总数、挥发性盐基氮值（total volatile base nitrogen,TVB-N）、pH值、硫代巴比妥酸值（the 2-thiobarbituric acid,TBA）和汁液流失率为指标,测定带鱼冷藏过程中的品质变化。结果表明：空气包装组带鱼冷藏货架期为4 d,复合生物保鲜剂（1.0%壳聚糖＋0.4%茶多酚）具有良好的抑菌保鲜作用,高浓度CO2气调包装带鱼汁液流失较为严重,生物保鲜剂结合60%CO2＋10%O2＋30%N2气调包装组保鲜效果最为显著,冷藏贮存20 d,带鱼的细菌总数为5.59 lg(cfu/g),TVB-N值为19.39 mg/100 g,仍处在带鱼二级鲜度之内,可将冷藏带鱼货架期延长至20d,是对照组的5倍,且能较好地维持新鲜带鱼感官品质,以期为带鱼的保鲜提供一定的参考。